DC-5a help please

DC-2, 3, 5, 10
50 Caliber

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boogietone
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Location: Dahne, AL

DC-5a help please

Post by boogietone » Sun Apr 20, 2014 8:22 pm

My beloved DC-5 is acting funny. Absolutely no problems with it but then today I turn it on and it sounds bad. Really bad. I swapped all tubes with a totally different set of tubes and it is exactly the same problem. Also, the channel masters on both channels are not working. All the other pots are working including the master/global volume. Forgot to check the reverb. I pulled the chassis and didn't see anything obvious. The amp has no mods that I know of except the serial EFX mod. So, long story longer, amp sounds very bad/brittle/no body and both channel masters do not do anything. The only volume control I have is the master volume. All other pots are working too (including gain and the pull boost) just no the channel masters. Any help be greatly appreciated.

Thanks in advance!
Guitars: HamerUSA T-62 and Centaura
Amp: Mesa DC-5a
EFX: Boss SD-1, DD-3

Orion_99
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Re: DC-5a help please

Post by Orion_99 » Sun Apr 20, 2014 8:56 pm

I am having a similar problem with my dc-3. Does it have very low output, like you can crank the main output knob and it's still quiet?
Something to try first off is jumper the fx loop. Just plug a one end of a cord into send and the other into the return. I've read lots about corroded connections on these jacks. If that doesn't work, run the cord from the send jack to the return of another amp. If you have the same weak signal through the other amp then you know the problem is in your preamp, like mine. Also run a cord from the send of another amp to the return of the dc-5. I found my power section was working fine by doing this.
I am currently searching for the component that is causing a short to ground in my dc-3. When I find out what it is I will let you know.
Good luck!

boogietone
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Re: DC-5a help please

Post by boogietone » Sun Apr 20, 2014 9:02 pm

My first hunch is an LDR or octocoupler? But I really don't have a clue. I'll try what you did tomorrow to narrow it down though. Thanks for the ideas!
Guitars: HamerUSA T-62 and Centaura
Amp: Mesa DC-5a
EFX: Boss SD-1, DD-3

Orion_99
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Posts: 17
Joined: Sun Apr 13, 2014 1:46 pm

Re: DC-5a help please

Post by Orion_99 » Sun Apr 20, 2014 11:43 pm

I pulled out the optocoupler in the recording out circuit out and my amp now works. I'm not sure if it was the problem or something else beyond it in the circuit, but I'll figure it out soon.

boogietone
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Re: DC-5a help please

Post by boogietone » Fri May 02, 2014 4:04 pm

Orion_99 wrote:I pulled out the optocoupler in the recording out circuit out and my amp now works. I'm not sure if it was the problem or something else beyond it in the circuit, but I'll figure it out soon.
Have you figured out anything else on your amp? Was it the octocoupler?
Guitars: HamerUSA T-62 and Centaura
Amp: Mesa DC-5a
EFX: Boss SD-1, DD-3

Orion_99
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Posts: 17
Joined: Sun Apr 13, 2014 1:46 pm

Re: DC-5a help please

Post by Orion_99 » Fri May 02, 2014 4:14 pm

I am waiting for the new op amp to arrive so I can see if it was the sole problem. I had to order them from China as my somewhat local supply store only carries tl082 not the 72. I tried the ne5532 from my dc-2 and although I seemed to get the correct voltages, I didn't get any output.

I will make sure to let you know as soon as I've figured it out.

boogietone
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Joined: Sat Aug 26, 2006 2:16 pm
Location: Dahne, AL

Re: DC-5a help please

Post by boogietone » Fri May 02, 2014 4:42 pm

Cool, thx.
Guitars: HamerUSA T-62 and Centaura
Amp: Mesa DC-5a
EFX: Boss SD-1, DD-3

Orion_99
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Posts: 17
Joined: Sun Apr 13, 2014 1:46 pm

Re: DC-5a help please

Post by Orion_99 » Thu May 08, 2014 5:20 pm

My new op amp arrived today. I popped it in and it works! I haven't checked voltages yet, but there's sound now when there wasn't before, so I'm happy. :D

boogietone
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Re: DC-5a help please

Post by boogietone » Fri May 09, 2014 10:42 am

That's awesome! I jumped the effects loop with a patch cord and it worked. So, now I'm waiting for a new jack to come in so I can replace the send jack. Thanks everyone and Monsta-tone!
Guitars: HamerUSA T-62 and Centaura
Amp: Mesa DC-5a
EFX: Boss SD-1, DD-3

boogietone
Donating Member
Posts: 697
Joined: Sat Aug 26, 2006 2:16 pm
Location: Dahne, AL

Re: DC-5a help please

Post by boogietone » Thu May 29, 2014 11:27 am

Orion_99 wrote:My new op amp arrived today. I popped it in and it works! I haven't checked voltages yet, but there's sound now when there wasn't before, so I'm happy. :D
Was the op amp hard to replace? Is your amp still working okay?
Guitars: HamerUSA T-62 and Centaura
Amp: Mesa DC-5a
EFX: Boss SD-1, DD-3

Orion_99
Bottle Rocket
Posts: 17
Joined: Sun Apr 13, 2014 1:46 pm

Re: DC-5a help please

Post by Orion_99 » Thu May 29, 2014 11:35 am

boogietone wrote:
Orion_99 wrote:My new op amp arrived today. I popped it in and it works! I haven't checked voltages yet, but there's sound now when there wasn't before, so I'm happy. :D
Was the op amp hard to replace? Is your amp still working okay?
It took about 30 seconds to replace it. You just have to pull the old one out of the holder and put the new one in. No soldering at all. The amp is working fine now. I only play at home so I haven't had it super loud, but so far so good.

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